i wasn't sure so to be sure i did two tests,
firstly the test on here
there is rumble through 10hz
but no sound/pitch or whatever you consider to be 'heard'
though here (test for harmonic distortion)
nothing, null sound, null rumble
by 16hz there is a slight rumble but it really doesn't feel like noise again i am trying to be put it how it feels as i dont see any way of better describing it.
the rumble is more visible and noticeable but its not like a car horn visible.
I agree with this,
usually 17khz is visible
under right condiitons the 18khz test is visible.
but my brain recognises something is going on at 18khz whether i hear it or not makes no difference.
to be sure, above 18khz i cant hear anything and my brain doesnt think there is anything going on
Edit: for quote and response
Interestingly enough I can hear the bottom row... Sounds like when you're driving on the highway and crack the back car window.